The goal of the Middle School to High School Transition Project is to extend a promising school-based program for the prevention of adolescent depression, school failure, and substance involvement during the critically important and challenging transition from middle school to high school. The preventive intervention, Coping and Support Training for the Transition (CAST-T), is a brief, skills-based program which begins with a 12-session (12 hr.) peer group model delivered to small groups of 6-7 students in the middle school setting over a 6-week period. Additionally, components of the intervention include booster sessions plus case management for students during the first semester of high school and a structured home-based parent education, support and skills training component spanning the transition period. The CAST-T curriculum addresses the primary risk factors associated with adolescent depression and school failure by enhancing personal efficacy and social support resources. The Middle School to High School Transition Project is a collaborative endeavor with Seattle Public Schools. Transition-vulnerable 8th grade students will be identified via a two-stage screening procedure. The first stage identifies school problem -vulnerable youth, and is based on school records of declining performance and poor attendance. The second stage identifies depression problem-vulnerable youth and is based on depression self-report scale scores. We plan to study 400 at-risk 8th graders from 5 large Seattle Public middle schools with 200 randomly assigned to each of the two conditions (CAST-T[E] or "school as usual" [C]. Each study participant (E&C) will undergo six assessments over a 15-month period beginning at the time of recruitment in the winter of 8th grade and ending in the spring of the 9th grade-freshman year of high school. The timing of the follow-up assessments will allow us to examine both short- and long-term intervention effectiveness. We hypothesize that students in the CAST-T condition will exhibit less depression, better school performance (grades, attendance, attitudes toward school), and less substance involvement. Further, students in the experimental group will experience enhanced self-efficacy (self-esteem, personal control, problem-solving coping) and social support resources (school, family, pro-social peer bonding) compared to control youth who are assigned to the school as usual condition. We will explore for gender and ethnic differences in outcomes and patterns of response to the CAST-T intervention. We will also conduct preliminary tests of a theoretically-specified causal model positing that the CAST-T intervention decreases depression, school problems, and progression of substance use through the mediating effects of enhanced self-efficacy and social support which in turn, attenuate the negative effects of antecedent risk factors such as vulnerable self-esteem, emotional dysregulation, emotion-focused coping, and other personal, family, and school vulnerabilities.